Studies On Cytotoxicity Of Cadmium Telluride Quantum Dots Prepared In Aquous Phase Using Human Cervical Cancer Cells As A Model

Quantum dots (QDs), also referred to as semiconductor nanocrystals, have drawn increasing attention in biological and medical fields due to their size-dependent and excellent optical properties such as high photoluminescent (PL) quantum yield, narrow emission profiles, broad excitation spectra, and good biocompatibility. But the toxicity of QDs remained an outstanding disadvantage. In this study, the cytotoxicity of CdTe QDs was evaluated using human cervical cancer SiHa cells as a model with WST-1 viability assay systematically considering their sizes, concentration, stablizers, exposure time and different surface modifications.Firstly, we prepared CdTe QDs with different emission wavelength using aqueous synthesis approach, and investigated the cytotoxicity of the QDs via WST-1 cell viability assay with SiHa cells. Our results revealed that CdTe QDs with glutathione (GSH) as a stabilizer was less toxic compared to CdTe QDs with 3-mercaptopropionic acid (MPA), dimercaptosuccinic acid (DMSA) and N-acetyl-L-cysteine (NAC). We also observed that the cell viability significantly decreased with smaller size of QDs, higher exposure concentration and longer exposure time. According to our calculation, the suface state might contribute a lot to the cytotoxicity of CdTe QDs.Secondly, surface modifications of CdTe QDs were conducted using bovine serum albumin (BSA), denatured bovine serum albumin (dBSA) and thiol polyethylene glycerol (PEG). We found that BSA-coated QDs and dBSA-coated QDs showed no reduction in cytotoxicity, but the PEG-coated QDs showed less cytotoxicity compared to the QDs core. After the coating of CdS and ZnS shell, the cytotoxicity of QDs decreased remarkably. Little reduction of cell viability was observed after 24 hours of CdTe/CdS/ZnS QDs exposure, and cell viability was 89.3% after 48 hours. Further investigation revealed that the release of Cd2+ from the CdTe core decreased remarkably after the coating of CdS and ZnS shell, which suggested the passivation shell of ZnS prevented the release of Cd2+ effectively, and optimized the surface state of CdTe QDs.